1. Field of the Invention
The present invention relates to a cone expansion wall plug, comprising a threaded rod or screw at one end, a tapped cone at the threaded end of the rod for expanding an expansible socket disposed about the rod and means adapted for immobilizing the socket, during expansion thereof against translation with respect to the rod and, after expansion of the socket, for allowing a translational movement of the rod with respect to the socket and so screwing of the rod into the cone.
Up to the moment when the expansion cone is immobilized, and with it the expansible socket, i.e. until the wall plug is anchored, the distance between the head of the screw and the expansible socket must remain practically constant otherwise the expansible socket may, during penetration of the cone, move towards the opening of the hole receiving the plug, which may affect the anchorage thereof. In other words, the expansible socket, during its expansion, must remain practically immobile in translation. Once the anchorage achieved, and the socket having in any case been moved slightly towards the opening of the hole receiving the plug during expansion thereof, that is to say that it has ridden up, it is necessary to firmly apply the part to be fixed by clamping it against the support material, in which the reception hole had been previously formed, by screwing the screw into the expansion cone which is then immobilized.
It will be noted that such a wall plug may serve for fixing any piece to a support material intended to receive it; it is a question preferably of heavy pieces to be fixed to hard materials, such as constructional materials for example.
2. Description of the Prior Art
The applicant has already proposed a wall plug of the above mentioned type, in which the immobilization means comprise a spacer disposed about the screw, between the head of the screw and the expansible socket, the socket being, at the outset, in abutment against a shearable collar of the spacer through an axial projecting portion.
But, for different reasons, among which lack of flexibility, during its expansion the expansible socket caused premature shearing of the collar of the spacer.
A wall plug of the above mentioned type is also known more particularly from French Pat. No. 1 592 228, in which the immobilization means comprise an intermediate ring between a spacer, in this case an enlarged diameter portion of the screw, and the expansible socket, and in abutment thereagainst, the intermediate ring being adapted so as to bend, after expansion of the socket, and so as to be deformed elastically, or swell, under the action of the screw screwed into the expansion cone.
But such a wall plug has the drawback that the intermediate ring, already during expansion of the socket and especially at the time of final locking, risks bending inwardly thus disturbing the screwing in and out of the screw.
The present invention brings then an improvement to this latter wall plug so as to overcome the disadvantage thereof.